gem-hunter

CachedImage component for react-native

This package is greatly inspired by @jayesbe's amazing react-native-cacheable-image but adds some functionality that we were missing when trying to handle caching images in our react-native app.

npm install react-native-cached-image --save
- or -
yarn add react-native-cached-image

We use react-native-fetch-blob to handle file system access in this package and it requires an extra step during the installation.

You should only have to do this once.

react-native link react-native-fetch-blob

Or, if you want to add Android permissions to AndroidManifest.xml automatically, use this one:

RNFB_ANDROID_PERMISSIONS=true react-native link react-native-fetch-blob

Add the following line to your android/app/src/AndroidManifest.xml

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

TODO - add usage example

import React from 'react';
import {
    CachedImage,
    ImageCacheProvider
} from 'react-native-cached-image';

const images = [
    'https://example.com/images/1.jpg',
    'https://example.com/images/2.jpg',
    'https://example.com/images/3.jpg',
    // ...
];

export default class Example extends React.Component {
    render() {
        return (
            <ImageCacheProvider
                urlsToPreload={images}
                onPreloadComplete={() => console.log('hey there')}>

                <CachedImage source={{uri: images[0]}}/>

                <CachedImage source={{uri: images[1]}}/>

                <CachedImage source={{uri: images[2]}}/>

            </ImageCacheProvider>
        );
    }
}

This package exposes 3 modules:

const {
    CachedImage,            // react-native component that is a drop-in replacement for your react-native `Image` components
    ImageCacheProvider,     // a top level component that provides accsess to the underlying `ImageCacheManager` and preloads images
    ImageCacheManager,      // the logic behind cache machanism - ttl, fs, url resolving etc. 
} = require('react-native-cached-image');

This is where all the cache magic takes place. The API usually takes a URL and a set of ImageCacheManagerOptions.

Check the cache for the the URL (after removing fixing the query string according to ImageCacheManagerOptions.useQueryParamsInCacheKey). If the URL exists in cache and is not expired, resolve with the local cached file path. Otherwise, download the file to the cache folder, add it to the cache and then return the cached file path.

Check the cache for the the URL (after removing fixing the query string according to ImageCacheManagerOptions.useQueryParamsInCacheKey). If the URL exists in cache and is not expired, resolve with the local cached file path. Otherwise, copy the seed file into the cache folder, add it to the cache and then return the cached file path.

Removes the cache entry for the URL and the local file corresponding to it, if it exists.

Clear the URL cache and remove files in the cache folder (as stated in the ImageCacheManagerOptions.cacheLocation)

Returns info about the cache, list of files and the total size of the cache.

CachedImage is a drop in replacement for the Image component that will attempt to cache remote URLs for better performance.
It's main use is to hide the cache layer from the user and provide a simple way to cache images.
CachedImage uses an instance of ImageCacheManager to interact with the cache, if there is an instance provided by ImageCacheProvider via the context it will be used, otherwise a new instance will be created with the options from the component's props.

<CachedImage
    source={{
        uri: 'https://example.com/path/to/your/image.jpg'
    }}
    style={styles.image}
/>

• renderImage - a function that returns a component, used to override the underlying Image component.
• activityIndicatorProps - props for the ActivityIndicator that is shown while the image is downloaded.
• defaultSource - prop to display a background image while the source image is downloaded. This will work even in android, but will not display background image if there you set borderRadius on this component style prop
• loadingIndicator - component prop to set custom ActivityIndicator.
• fallbackSource - prop to set placeholder image. when source.uri is null or cached failed, the fallbackSource will be display.
• any of the ImageCacheManagerOptionsPropTypes props - customize the ImageCacheManager for this specific CachedImage instance.

This is a top-level component with 2 major functions:

1. Provide the customized ImageCacheManager to nested CachedImage.
2. Preload a set of URLs.

• urlsToPreload - an array of URLs to preload when the component mounts. default []
• numberOfConcurrentPreloads - control the number of concurrent downloads, usually used when the urlsToPreload array is very big. default urlsToPreload.length
• onPreloadComplete - callback for when the preload is complete and all images are cached.

A set of options that are provided to the ImageCacheManager and provide ways to customize it to your needs.

type ImageCacheManagerOptions = {
    headers: PropTypes.object,                      // an object to be used as the headers when sending the request for the url. default {}
    
    ttl: PropTypes.number,                          // the number of seconds each url will stay in the cache. default 2 weeks
    
    useQueryParamsInCacheKey: PropTypes.oneOfType([ // when handling a URL with query params, this indicates how it should be treated:
        PropTypes.bool,                             // if a bool value is given the whole query string will be used / ignored
        PropTypes.arrayOf(PropTypes.string)         // if an array of strings is given, only these keys will be taken from the query string.
    ]),                                             // default false
    
    cacheLocation: PropTypes.string,                // the path to the root of the cache folder. default the device cache dir 
    
    allowSelfSignedSSL: PropTypes.bool,             // true to allow self signed SSL URLs to be downloaded. default false
};

Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.